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IP addressing
Számítógép networkok gyakorlata
ÓBUDAI EGYETEM
2011 TAVASZI FÉLÉV
3. LABORGYAKORLAT
PRÉM DÁNIEL
IP address
172
.
16
.
254
.
1
10101100
.
00010000
.
11111110
.
00000001
• Logical addressing
• 32 bit integer
• IP address can be split into two parts:
network and host ID
IP address properties
• Network ID is the same at each host inone
network. Host ID has to be different
• Routers use the network ID when
forwarding packages.
• One host can have multiple interfaces –
each interface connects to a different
network
History of IP classes
• Back in the dark ages the first 8 bits were the
network ID, the rest was the host id
• It was realized soon how smal that number is.
• In 1981 the Classful Network achitecture was
created. It described 5 classes that were self
explanatory from the IP address (A, B, C, D, E)
• Scalability was an issue even using this
architecture, so in 1993 ”Classless InterDomain Routing” (CIDR) architecture was
invented which uses variable length network ID
IP address classes
Classful Network
A class
0
network
B class
1 0
C class
1 1 0
D class
1 1 1 0
E class
1 1 1 1 0
host
network
host
network
host
multicast
reserved
Class
Leading bits
First octet
Number of
networks
Number of hosts
A class
0
0 – 127
27 = 128
224 = 16.777.216
B class
10
128 – 191
214 = 16.384
216 = 65.536
C class
110
192 – 223
221 = 2.097.152
28 = 256
D class
1110
224 – 239
–
–
E class
11110
240 – 255
–
–
Private IP ranges
• Often it is necessary to connect devices to the network, but
not to the internet. RFC 1918 manages the private IP
addresses that cannot appear on the internet, but are
reserved for private use.
• Private IP ranges managed by IANA:
Class
From
1 x A class
10.0.0.0
16 x B class
172.16.0.0
256 x C class
To
No. Of hosts
10.255.255.255 224 = 16.777.216
172.31.255.255 220 = 1.048.576
192.168.0.0 192.168.255.255 216 = 65.536
• example:
- 192.168.1.0/24 (mask: 255.255.255.0 | 256 hosts) - 256 networks
- 172.17.0.0/16 (mask: 255.255.0.0 | 65.536 hosts) 256 networks
Virtual network interface
• Sometimes it is necessary for hosts to provide services that have to be
used by itself.
• Such services are provided through the loopback network.
• The loopback device is implemented in software only
• Canniot appear on the web
Classcíme a localhost
first network
last network
• Speciális
ami a 127.0.0.1
IP cím.
address
1 x A class
number of hosts
address
127.0.0.0 127.255.255.255 224 = 16.777.216
Network and broadcast addresses
• networki cím:
IP address full of zeroes
– xx.xx.xx.0
• Broadcast cím:
IP address full of ones
– xx.xx.xx.255
Subnet mask
• Further subcategorize the network
• 32 bit number
Subnet mask example
• 192.168.0.0/24 [mask: 255.255.255.0]
network id
192.168.0.0
range
Broadcast
addr.
Állomások száma
192.168.0.1 – 192.168.0.254 192.168.0.255
253
• 192.168.0.0/22 [maszk: 255.255.252.0]
network id
192.168.0.0
range
Broadcast
addr
Állomások száma
192.168.0.1 – 192.168.3.254 192.168.3.255
1022
• 192.198.0.0/26 [maszk: 255.255.255.192]
network id
range
Broadcast
addr
Állomások száma
192.168.0.0
192.168.0.1 – 192.168.0.62
192.168.3.63
61
Címzési módok
• Unicast:
Egy az egynek kapcsolat
Minden cím egyedi és központilag kiosztott, emiatt
egyértelműen azonosítja a címzettet.
• Multicast:
Egy a többnek kapcsolat
Lehetővé teszi az adó számára, hogy az üzenete több
címzetthez is eljusson.
• Broadcast:
Egy mindenkinek kapcsolat
A multicast speciális esete, ekkor mindenkinek szól az
üzenet, így a network összes eleme beolvassa a csomagot.